This invention relates to a countermeasure system for protecting jet aircraft and missiles from detection by missile and ground-base infrared detection systems. More particularly, this invention contains itself with a high temperature, low emittance, camouflage coating system which, when applied to the strategic surfaces of aircraft jet engines and missile components, will effectively reduce their level of emitted energy and render them undetectable by missile and ground base detection systems.
Tactical aircraft are prime targets for a variety of infrared seeking missiles and other infrared detection devices. While cruising at altitude or during a low level attack, they are especially vulnerable to air launched missiles such as the Sidewinder or Falcon. In a close support mission, ground launched missiles, like Redeye, provide a very effective defense. The very low cost, ease of operation and the extremely high reliability of these IR missiles make them a threat in all categories of war where tactical aircraft are used.
The feasibility of using low emissivity coatings to suppress the infrared signature of external jet engine components has been demonstrated. The demonstration showed that a low emissivity coating on an external nozzle plug reduced the IR signature for that component significantly. It has been suggested that further suppression can be realized by controlling surface emissivities of internal exhaust system components. For application to advanced jet engines, and particularly for countermeasure purposes, a judicious selection of high and low emissivity coating surfaces on critical components is required to optimize the trade-off between emission and reflection.
The missile's capability to seek and destroy could be nullified if the intensity of engine radiation could be decreased in the missile detector's wavelength and bandwidth of response and the radiation emitted from the engine could be shifted to wavelengths outside of the response range of missile detectors. Ultimately, the reduction of the IR signature requires both the incorporation of efficient cooled exhaust system components and the development of optically, chemically, and mechanically stable emissive/reflective surfaces for them. These must be applicable to existing as well as future turbojet or turbofan engines.
As a consequence, a considerable research effort has evolved in an attempt to develop countermeasures or camouflage materials which, when applied to the strategic surfaces of aircraft jet engines, will effectively reduce their level of emitted energy and render them undetectable by missile and ground-base detection systems. It is important that the dimunition be restricted as much as possible to the 1-6 micron wavelength region, and that the bulk of the radiation be allowed to propagate freely from the aircraft in the other wavelength regimes.
For application to advanced jet engines, and particularly for countermeasure purposes, a judicious selection of high and low emissivity surfaces on critical components is required to optimize the trade-off between emission and reflection. Also, the air-breathing environment limits the utility of coatings previously acceptable for thermal control of space oriented systems. The rigors a coating must endure to operate successfully in a jet engine environment include the influences of thermally induced stress, overtemperature, corrosion, foreign object impact, and the metallurgical instability of coatings. These factors have provided a deterring influence on the use of prior art systems.
In furtherance of the research effort referred to above, and in an attempt to provide a system for preventing infrared detection, it was found that a composite, low emissivity coating system composed of a diffusion barrier coating, a reflective metal coating and a protective overlay coating could be applied to the metal surfaces of jet engine components. The application of the composite coating of this invention to the surfaces of the engine components effectively reduces their level of emitted energy thereby rendering them undetectable by infrared detection systems.